Ultrasonic measuring method and ultrasonic measuring apparatus

Abstract

An ultrasonic measuring method includes: (A) receiving a coded spread spectrum ultrasonic signal in at least two receivers, and generating at least two received signals; (B) performing an quadrature detection on the received signals using the carrier frequency, and producing I and Q components of the received signals; (C) performing phase difference processing on the I and Q components with a coding period synchronized with that of the carrier frequency, and obtaining I′ and Q′ components from which a phase shift caused by a Doppler shift has been canceled; (D) despreading the I′ and Q′ components signals using different codes at time intervals synchronized with the carrier frequency, and obtaining despread I″ and Q″ components; (E) computing the amplitude and phase information based on the I″ and Q″ components; and (F) calculating the propagation distance and / or orientation of the ultrasonic wave based on the amplitude and phase information.

Description

[0001]This is a continuation of International Application No. PCT / JP2011 / 000871, with an international filing date of Feb. 17, 2011, which claims priority of Japanese Patent Application No. 2010-033112, filed on Feb. 18, 2010, the contents of which are hereby incorporated by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a method and apparatus for ultrasonic measuring. More particularly, the present invention relates to a measuring method and apparatus that can accurately estimate the propagation distance or propagation direction of an ultrasonic wave by using a spread spectrum coded ultrasonic wave even when there is a relative velocity between the object of measurement and the measuring apparatus.[0004]2. Description of the Related Art[0005]An ultrasonic measuring apparatus includes a transmitter to send out an ultrasonic wave and a receiver to receive the ultrasonic wave and estimates the distance between the transmitter...

AI Technical Summary

Benefits of technology

[0020]It is therefore an object of the present invention to provide an ultrasonic measuring apparatus and method that can get measurements done accurately through simple processing even when the ultrasonic measuring apparatus should operate in an environment where it can be affected by an unspecified large number of Doppler shifts.

[0031]According to the present invention, an quadrature detection signal of a received signal is processed with a coding period that is synchronized with the carrier frequency, thereby canceling the Doppler shift. Also, the despreading process is carried out using different codes from what has been used for transmission, thereby obtaining a despread signal with as high an SNR as if no Doppler shift were produced at all. On top of that, in that case, there may be multiple Doppler shifts (i.e., reflectors with mutually different relative velocities) within a predetermined Doppler shift range. Consequently, according to the present invention, the distance to the object or its orientation can be estimated accurately with the Doppler shift effect reduced significantly even without measuring the Doppler shift itself.

Problems solved by technology

In an environment where there are a number of such ultrasonic measuring apparatuses, the ultrasonic waves transmitted simultaneously by the respective ultrasonic measuring apparatuses would interfere with each other, thus possibly causing measurement errors.

If a Doppler shift is produced, however, the peak of correlation will decrease significantly and the correlation noise in the ranges before and after the peak will also have raised levels.

As a result, the SNR will drop steeply.

According to that method, however, it is still difficult to compensate for the Doppler shift perfectly and recover the correlation gain.

As a result, the size and cost of the hardware to use will rise too much to apply that technique to a consumer electronic device easily.

That is why to get the compensation done, a lot of memory space and processing time are needed.

However, such a method should not be applied to processing that requires high speed response such as sensing an obstacle for a self-moving robot.

Furthermore, in sensing an obstacle for a self-moving robot, for example, generally there are an unspecified large number of objects to sense, which will include objects (such as persons) that move at various relative velocities.

Consequently, as there will be a mixture of various relative velocities between the self-moving robot and the objects of sensing, it is difficult to apply the method disclosed in Japanese Patent Application Laid-Open Publication No. 2007-202088 that uses a compensating signal on an individual basis to such a situation.

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